Several different types of blowing lances are used in the refining of steel. They are usually suspended vertically and fixed to a movable carriage. Flexible pipes carry cooling and blowing fluids to the lance through a connector arrangement having rigid tubes welded to the body of the lance. In order to change or clean a lance it is necessary to uncouple the several tubes, disconnect the lance from its support, and thereafter transport it to the shop.
The disconnection of the various pipes is, however, a considerable job. Thus if only one lance-carrying carriage is provided substantial time can be lost in the mounting operation. In view of the time necessary to replace the lance the general practice is to have a second lance in reserve which is used during the complicated dismounting and refurbishing operation. In any case the cleaning operation is much too complicated and lengthy to be carried out merely during the pauses in the blowing operation.
The lance is usually changed with the head carrying the tubes and the various connectors. When, as is frequently the case, the lance can no longer be refurbished and reused it is necessary to discard the entire assembly. Since this assembly is extremely expensive, as it must be built to very close tolerances and of relatively costly materials, its replacement considerably increases production costs.
It is absolutely essential, however, that there be no leakage from the lance or its supply head. It is for this reason that hitherto nothing has been used except welded, brazed, and soldered joints in the construction of the lance assembly. It has been suggested to use a telescoping type of lance, but the problem of sealing such an assembly has been so considerable that either a very expensive unit was required, or a very short service life was obtained.